Exponential decay of spin-spin correlation between distant defect states produced by contour hydrogenation of polycyclic aromatic hydrocarbon molecules

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Títol: Exponential decay of spin-spin correlation between distant defect states produced by contour hydrogenation of polycyclic aromatic hydrocarbon molecules
Autors: Chiappe, Guillermo | Louis, Enrique | Guijarro, Albert | San-Fabián, Emilio | Vergés Brotons, José Antonio
Grups d'investigació o GITE: Física de la Materia Condensada | Materiales Avanzados | Nuevos Materiales y Catalizadores (MATCAT) | Química Cuántica
Centre, Departament o Servei: Universidad de Alicante. Departamento de Física Aplicada | Universidad de Alicante. Departamento de Química Orgánica | Universidad de Alicante. Departamento de Química Física
Paraules clau: Polycyclic aromatic hydrocarbon molecules | Defect states | Contour hydrogenation | Spin-spin correlation | Ab initio
Àrees de coneixement: Física Aplicada | Física de la Materia Condensada | Química Orgánica | Química Física
Data de publicació: 18-de març-2013
Editor: American Physical Society
Citació bibliogràfica: Phys. Rev. B. 2013, 87: 125126 [10 pages]. doi:10.1103/PhysRevB.87.125126
Resum: The first few low-lying spin states of alternant polycyclic aromatic hydrocarbon (PAH) molecules of several shapes showing defect states induced by contour hydrogenation have been studied both by ab initio methods and by a precise numerical solution of Pariser-Parr-Pople (PPP) interacting model. In accordance with Lieb's theorem, the ground state shows a spin multiplicity equal to one for balanced molecules, and it gets larger values for imbalanced molecules (that is, when the number of π electrons on both subsets is not equal). Furthermore, we find a systematic decrease of the singlet-triplet splitting as a function of the distance between defects, regardless of whether the ground state is singlet or triplet. For example, a splitting smaller than 0.001 eV is obtained for a medium size C46H28 PAH molecule (di-hydrogenated [11]phenacene) showing a singlet ground state. We conclude that π electrons unbound by lattice defects tend to remain localized and unpaired even when long-range Coulomb interaction is taken into account. Therefore they show a biradical character (polyradical character for more than two defects) and should be studied as two or more local doublets. The implications for electron transport are potentially important since these unpaired electrons can trap traveling electrons or simply flip their spin at a very small energy cost.
Patrocinadors: Financial support by the Spanish MICINN (MAT2011-26534, CTQ2007-65218, CSD2007-6, FIS2009-08744, and CTQ2011-24165) and the Universidad de Alicante; support from the DGUI of the Comunidad de Madrid under the R&D Program of activities MODELICO-CM/S2009ESP-1691.
URI: http://hdl.handle.net/10045/33595
ISSN: 1098-0121 (Print) | 1550-235X (Online)
DOI: 10.1103/PhysRevB.87.125126
Idioma: eng
Tipus: info:eu-repo/semantics/article
Drets: ©2013 American Physical Society
Revisió científica: si
Versió de l'editor: http://dx.doi.org/10.1103/PhysRevB.87.125126
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